In a vehicle such as an automotive vehicle, there has been generally known a technique of setting a target acceleration characteristic in such a manner that a target acceleration of the vehicle become larger along with an increase in amount of depression of an accelerator pedal operated by a driver (accelerator angle), and controlling engine output torque to achieve the set target acceleration characteristic.
In connection with the technique of setting such a target acceleration characteristic, for example, JP 2007-247579A discloses setting a target acceleration based on an accelerator angle-target acceleration correlation preset in such a manner that the target acceleration becomes larger as an increase in the accelerator angle, and an accelerator angle detection value to be sequentially input.
Meanwhile, a level of required acceleration for a vehicle is generally higher in a low vehicle speed region than in a high vehicle speed region. Thus, it is desirable to set the target acceleration characteristic in such a manner that the target acceleration becomes smaller along with an increase in the vehicle speed, even under the same condition in terms of the accelerator angle. This makes it possible to realize high fuel economy performance in the high vehicle speed region while enhancing accelerating performance in the low vehicle speed region.
Further, even under the same conditions in terms of the vehicle speed and the accelerator angle, a level of acceleration sensuously evaluated as adequate varies depending on whether or not a driver has an aggressive intention. For example, it is considered that an aggressive driver intends to accelerate a vehicle at a higher acceleration, mainly in low and medium vehicle speed regions. However, continually setting the target acceleration characteristic in a relatively high acceleration region to suit aggressive drivers will lead to deterioration in fuel economy performance.